mirror of
https://github.com/metabolist/metatext.git
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437 lines
18 KiB
Swift
437 lines
18 KiB
Swift
// Copyright © 2020 Metabolist. All rights reserved.
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import Combine
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import Foundation
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import Mastodon
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import ServiceLayer
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// swiftlint:disable file_length
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public class CollectionItemsViewModel: ObservableObject {
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public let identityContext: IdentityContext
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@Published public var alertItem: AlertItem?
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public private(set) var nextPageMaxId: String?
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@Published private var lastUpdate = CollectionUpdate(
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sections: [],
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maintainScrollPositionItemId: nil,
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shouldAdjustContentInset: false)
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private let collectionService: CollectionService
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private var viewModelCache = [CollectionItem: (viewModel: CollectionItemViewModel, events: AnyCancellable)]()
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private let eventsSubject = PassthroughSubject<CollectionItemEvent, Never>()
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private let loadingSubject = PassthroughSubject<Bool, Never>()
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private let expandAllSubject: CurrentValueSubject<ExpandAllState, Never>
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private var topVisibleIndexPath = IndexPath(item: 0, section: 0)
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private let lastReadId = CurrentValueSubject<String?, Never>(nil)
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private var lastSelectedLoadMore: LoadMore?
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private var hasRequestedUsingMarker = false
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private var shouldRestorePositionOfLocalLastReadId = false
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private var cancellables = Set<AnyCancellable>()
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public init(collectionService: CollectionService, identityContext: IdentityContext) {
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self.collectionService = collectionService
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self.identityContext = identityContext
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expandAllSubject = CurrentValueSubject(
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collectionService is ContextService && !identityContext.identity.preferences.readingExpandSpoilers
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? .expand : .hidden)
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collectionService.sections
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.handleEvents(receiveOutput: { [weak self] in self?.process(sections: $0) })
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.receive(on: DispatchQueue.main)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.sink { _ in }
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.store(in: &cancellables)
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collectionService.nextPageMaxId
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.sink { [weak self] in self?.nextPageMaxId = $0 }
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.store(in: &cancellables)
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if let markerTimeline = collectionService.markerTimeline {
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shouldRestorePositionOfLocalLastReadId =
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identityContext.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .rememberPosition
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lastReadId.compactMap { $0 }
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.removeDuplicates()
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.debounce(for: .seconds(Self.lastReadIdDebounceInterval), scheduler: DispatchQueue.global())
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.flatMap { identityContext.service.setLastReadId($0, forMarker: markerTimeline) }
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.sink { _ in } receiveValue: { _ in }
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.store(in: &cancellables)
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}
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}
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public var updates: AnyPublisher<CollectionUpdate, Never> {
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$lastUpdate.eraseToAnyPublisher()
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}
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public func requestNextPage(fromIndexPath indexPath: IndexPath) {
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guard let maxId = collectionService.preferLastPresentIdOverNextPageMaxId
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? lastUpdate.sections[indexPath.section].items[indexPath.item].itemId
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: nextPageMaxId
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else { return }
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request(maxId: maxId, minId: nil, search: nil)
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}
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}
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extension CollectionItemsViewModel: CollectionViewModel {
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public var title: AnyPublisher<String, Never> { collectionService.title }
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public var titleLocalizationComponents: AnyPublisher<[String], Never> {
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collectionService.titleLocalizationComponents
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}
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public var expandAll: AnyPublisher<ExpandAllState, Never> {
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expandAllSubject.eraseToAnyPublisher()
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}
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public var alertItems: AnyPublisher<AlertItem, Never> { $alertItem.compactMap { $0 }.eraseToAnyPublisher() }
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public var loading: AnyPublisher<Bool, Never> { loadingSubject.eraseToAnyPublisher() }
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public var events: AnyPublisher<CollectionItemEvent, Never> { eventsSubject.eraseToAnyPublisher() }
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public var canRefresh: Bool { collectionService.canRefresh }
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public func request(maxId: String? = nil, minId: String? = nil, search: Search?) {
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let publisher: AnyPublisher<Never, Error>
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if let markerTimeline = collectionService.markerTimeline,
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identityContext.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .syncPosition,
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!hasRequestedUsingMarker {
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publisher = identityContext.service.getMarker(markerTimeline)
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.flatMap { [weak self] in
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self?.collectionService.request(maxId: $0.lastReadId, minId: nil, search: nil)
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?? Empty().eraseToAnyPublisher()
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}
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.catch { [weak self] _ in
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self?.collectionService.request(maxId: nil, minId: nil, search: nil)
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?? Empty().eraseToAnyPublisher()
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}
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.collect()
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.flatMap { [weak self] _ in
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self?.collectionService.request(maxId: nil, minId: nil, search: nil)
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?? Empty().eraseToAnyPublisher()
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}
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.eraseToAnyPublisher()
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self.hasRequestedUsingMarker = true
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} else {
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publisher = collectionService.request(maxId: realMaxId(maxId: maxId), minId: minId, search: search)
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}
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publisher
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.receive(on: DispatchQueue.main)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.handleEvents(
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receiveSubscription: { [weak self] _ in self?.loadingSubject.send(true) },
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receiveCompletion: { [weak self] _ in self?.loadingSubject.send(false) })
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.sink { _ in }
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.store(in: &cancellables)
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}
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public func select(indexPath: IndexPath) {
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let item = lastUpdate.sections[indexPath.section].items[indexPath.item]
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switch item {
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case let .status(status, _):
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eventsSubject.send(
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.navigation(.collection(collectionService
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.navigationService
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.contextService(id: status.displayStatus.id))))
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case let .loadMore(loadMore):
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lastSelectedLoadMore = loadMore
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(viewModel(indexPath: indexPath) as? LoadMoreViewModel)?.loadMore()
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case let .account(account, _):
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eventsSubject.send(
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.navigation(.profile(collectionService
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.navigationService
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.profileService(account: account))))
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case let .notification(notification, _):
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if let status = notification.status {
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eventsSubject.send(
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.navigation(.collection(collectionService
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.navigationService
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.contextService(id: status.displayStatus.id))))
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} else {
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eventsSubject.send(
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.navigation(.profile(collectionService
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.navigationService
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.profileService(account: notification.account))))
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}
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case let .conversation(conversation):
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guard let status = conversation.lastStatus else { break }
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eventsSubject.send(
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.navigation(.collection(collectionService
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.navigationService
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.contextService(id: status.displayStatus.id))))
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case let .tag(tag):
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eventsSubject.send(
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.navigation(.collection(collectionService
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.navigationService
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.timelineService(timeline: .tag(tag.name)))))
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case let .moreResults(moreResults):
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eventsSubject.send(.navigation(.searchScope(moreResults.scope)))
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}
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}
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public func viewedAtTop(indexPath: IndexPath) {
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topVisibleIndexPath = indexPath
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if !shouldRestorePositionOfLocalLastReadId,
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lastUpdate.sections.count > indexPath.section,
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lastUpdate.sections[indexPath.section].items.count > indexPath.item {
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lastReadId.send(lastUpdate.sections[indexPath.section].items[indexPath.item].itemId)
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}
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}
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public func canSelect(indexPath: IndexPath) -> Bool {
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switch lastUpdate.sections[indexPath.section].items[indexPath.item] {
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case let .status(_, configuration):
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return !configuration.isContextParent
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case .loadMore:
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return !((viewModel(indexPath: indexPath) as? LoadMoreViewModel)?.loading ?? false)
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default:
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return true
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}
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}
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// swiftlint:disable:next function_body_length cyclomatic_complexity
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public func viewModel(indexPath: IndexPath) -> CollectionItemViewModel {
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let item = lastUpdate.sections[indexPath.section].items[indexPath.item]
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let cachedViewModel = viewModelCache[item]?.viewModel
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switch item {
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case let .status(status, configuration):
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let viewModel: StatusViewModel
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if let cachedViewModel = cachedViewModel as? StatusViewModel {
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viewModel = cachedViewModel
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} else {
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viewModel = .init(
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statusService: collectionService.navigationService.statusService(status: status),
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identityContext: identityContext)
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cache(viewModel: viewModel, forItem: item)
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}
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viewModel.configuration = configuration
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return viewModel
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case let .loadMore(loadMore):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = LoadMoreViewModel(
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loadMoreService: collectionService.navigationService.loadMoreService(loadMore: loadMore))
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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case let .account(account, configuration):
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let viewModel: AccountViewModel
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if let cachedViewModel = cachedViewModel as? AccountViewModel {
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viewModel = cachedViewModel
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} else {
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viewModel = AccountViewModel(
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accountService: collectionService.navigationService.accountService(account: account),
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identityContext: identityContext)
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cache(viewModel: viewModel, forItem: item)
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}
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viewModel.configuration = configuration
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return viewModel
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case let .notification(notification, statusConfiguration):
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let viewModel: CollectionItemViewModel
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if let cachedViewModel = cachedViewModel {
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viewModel = cachedViewModel
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} else if let status = notification.status, let statusConfiguration = statusConfiguration {
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let statusViewModel = StatusViewModel(
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statusService: collectionService.navigationService.statusService(status: status),
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identityContext: identityContext)
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statusViewModel.configuration = statusConfiguration
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viewModel = statusViewModel
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cache(viewModel: viewModel, forItem: item)
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} else {
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viewModel = NotificationViewModel(
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notificationService: collectionService.navigationService.notificationService(
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notification: notification),
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identityContext: identityContext)
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cache(viewModel: viewModel, forItem: item)
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}
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return viewModel
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case let .conversation(conversation):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = ConversationViewModel(
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conversationService: collectionService.navigationService.conversationService(
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conversation: conversation),
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identityContext: identityContext)
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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case let .tag(tag):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = TagViewModel(tag: tag)
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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case let .moreResults(moreResults):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = MoreResultsViewModel(moreResults: moreResults)
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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}
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}
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public func toggleExpandAll() {
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let statusIds = Set(lastUpdate.sections.map(\.items).reduce([], +).compactMap { item -> Status.Id? in
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guard case let .status(status, _) = item else { return nil }
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return status.id
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})
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switch expandAllSubject.value {
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case .hidden:
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break
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case .expand:
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(collectionService as? ContextService)?.expand(ids: statusIds)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.collect()
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.sink { [weak self] _ in self?.expandAllSubject.send(.collapse) }
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.store(in: &cancellables)
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case .collapse:
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(collectionService as? ContextService)?.collapse(ids: statusIds)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.collect()
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.sink { [weak self] _ in self?.expandAllSubject.send(.expand) }
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.store(in: &cancellables)
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}
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}
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public func applyAccountListEdit(viewModel: AccountViewModel, edit: CollectionItemEvent.AccountListEdit) {
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(collectionService as? AccountListService)?.remove(id: viewModel.id)
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switch edit {
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case .acceptFollowRequest, .rejectFollowRequest:
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identityContext.service.verifyCredentials()
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.sink { _ in }
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.store(in: &cancellables)
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}
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}
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}
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private extension CollectionItemsViewModel {
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private static let lastReadIdDebounceInterval: TimeInterval = 0.5
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var lastUpdateWasContextParentOnly: Bool {
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collectionService is ContextService && lastUpdate.sections.map(\.items).map(\.count) == [0, 1, 0]
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}
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func cache(viewModel: CollectionItemViewModel, forItem item: CollectionItem) {
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viewModelCache[item] = (viewModel, viewModel.events
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.flatMap { [weak self] events -> AnyPublisher<CollectionItemEvent, Never> in
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guard let self = self else { return Empty().eraseToAnyPublisher() }
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return events.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.eraseToAnyPublisher()
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}
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.sink { [weak self] in self?.eventsSubject.send($0) })
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}
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func process(sections: [CollectionSection]) {
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let items = sections.map(\.items).reduce([], +)
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let itemsSet = Set(items)
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self.lastUpdate = .init(
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sections: sections,
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maintainScrollPositionItemId: idForScrollPositionMaintenance(newSections: sections),
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shouldAdjustContentInset: lastUpdateWasContextParentOnly && items.count > 1)
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viewModelCache = viewModelCache.filter { itemsSet.contains($0.key) }
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}
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func realMaxId(maxId: String?) -> String? {
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guard let maxId = maxId else { return nil }
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guard let markerTimeline = collectionService.markerTimeline,
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identityContext.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .rememberPosition,
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let lastItemId = lastUpdate.sections.last?.items.last?.itemId
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else { return maxId }
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return min(maxId, lastItemId)
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}
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func idForScrollPositionMaintenance(newSections: [CollectionSection]) -> CollectionItem.Id? {
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let items = lastUpdate.sections.map(\.items).reduce([], +)
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let newItems = newSections.map(\.items).reduce([], +)
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if shouldRestorePositionOfLocalLastReadId,
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let markerTimeline = collectionService.markerTimeline,
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let localLastReadId = identityContext.service.getLocalLastReadId(markerTimeline),
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newItems.contains(where: { $0.itemId == localLastReadId }) {
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shouldRestorePositionOfLocalLastReadId = false
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return localLastReadId
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}
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if collectionService is ContextService,
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lastUpdate.sections.isEmpty || lastUpdate.sections.map(\.items.count) == [0, 1, 0],
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let contextParent = newItems.first(where: {
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guard case let .status(_, configuration) = $0 else { return false }
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return configuration.isContextParent // Maintain scroll position of parent after initial load of context
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}) {
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return contextParent.itemId
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} else if collectionService is TimelineService {
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let difference = newItems.difference(from: items)
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if let lastSelectedLoadMore = lastSelectedLoadMore {
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for removal in difference.removals {
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if case let .remove(_, item, _) = removal,
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case let .loadMore(loadMore) = item,
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loadMore == lastSelectedLoadMore,
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let direction = (viewModelCache[item]?.viewModel as? LoadMoreViewModel)?.direction,
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direction == .up,
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let statusAfterLoadMore = items.first(where: {
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guard case let .status(status, _) = $0 else { return false }
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return status.id == loadMore.beforeStatusId
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}) {
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return statusAfterLoadMore.itemId
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}
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}
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}
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if lastUpdate.sections.count > topVisibleIndexPath.section,
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lastUpdate.sections[topVisibleIndexPath.section].items.count > topVisibleIndexPath.item {
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let topVisibleItem = lastUpdate.sections[topVisibleIndexPath.section].items[topVisibleIndexPath.item]
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if newSections.count > topVisibleIndexPath.section,
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let newIndex = newSections[topVisibleIndexPath.section]
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.items.firstIndex(where: { $0.itemId == topVisibleItem.itemId }),
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newIndex > topVisibleIndexPath.item {
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return topVisibleItem.itemId
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}
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}
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}
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return nil
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}
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}
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// swiftlint:enable file_length
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